/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hbase.io;

import java.io.*;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import org.apache.commons.logging.Log;

import org.apache.hadoop.hbase.conf.Configuration;

/**
 * An utility class for I/O related functionality. 
 */
public class IOUtils {

	/**
	 * Copies from one stream to another.
	 * @param in InputStrem to read from
	 * @param out OutputStream to write to
	 * @param buffSize the size of the buffer 
	 * @param close whether or not close the InputStream and 
	 * OutputStream at the end. The streams are closed in the finally clause.  
	 */
	public static void copyBytes(InputStream in, OutputStream out, int buffSize, boolean close) throws IOException {

		try {
			copyBytes(in, out, buffSize);
		} finally {
			if (close) {
				out.close();
				in.close();
			}
		}
	}

	/**
	 * Copies from one stream to another.
	 * 
	 * @param in InputStrem to read from
	 * @param out OutputStream to write to
	 * @param buffSize the size of the buffer 
	 */
	public static void copyBytes(InputStream in, OutputStream out, int buffSize) throws IOException {

		PrintStream ps = out instanceof PrintStream ? (PrintStream) out : null;
		byte buf[] = new byte[buffSize];
		int bytesRead = in.read(buf);
		while (bytesRead >= 0) {
			out.write(buf, 0, bytesRead);
			if ((ps != null) && ps.checkError()) {
				throw new IOException("Unable to write to output stream.");
			}
			bytesRead = in.read(buf);
		}
	}

	/**
	 * Copies from one stream to another. <strong>closes the input and output streams 
	 * at the end</strong>.
	 * @param in InputStrem to read from
	 * @param out OutputStream to write to
	 * @param conf the Configuration object 
	 */
	public static void copyBytes(InputStream in, OutputStream out, Configuration conf) throws IOException {
		copyBytes(in, out, conf.getInt("io.file.buffer.size", 4096), true);
	}

	/**
	 * Copies from one stream to another.
	 * @param in InputStrem to read from
	 * @param out OutputStream to write to
	 * @param conf the Configuration object
	 * @param close whether or not close the InputStream and 
	 * OutputStream at the end. The streams are closed in the finally clause.
	 */
	public static void copyBytes(InputStream in, OutputStream out, Configuration conf, boolean close) throws IOException {
		copyBytes(in, out, conf.getInt("io.file.buffer.size", 4096), close);
	}

	/**
	 * Copies the specified length of bytes from in to out.
	 *
	 * @param in InputStream to read from
	 * @param out OutputStream to write to
	 * @param length number of bytes to copy
	 * @param bufferSize the size of the buffer 
	 * @param close whether to close the streams
	 * @throws IOException if bytes can not be read or written
	 */
	public static void copyBytes(InputStream in, OutputStream out, final long length, final int bufferSize, final boolean close)
			throws IOException {
		final byte buf[] = new byte[bufferSize];
		try {
			int n = 0;
			for (long remaining = length; remaining > 0 && n != -1; remaining -= n) {
				final int toRead = remaining < buf.length ? (int) remaining : buf.length;
				n = in.read(buf, 0, toRead);
				if (n > 0) {
					out.write(buf, 0, n);
				}
			}

			if (close) {
				out.close();
				out = null;
				in.close();
				in = null;
			}
		} finally {
			if (close) {
				closeStream(out);
				closeStream(in);
			}
		}
	}

	/** Reads len bytes in a loop.
	 * @param in The InputStream to read from
	 * @param buf The buffer to fill
	 * @param off offset from the buffer
	 * @param len the length of bytes to read
	 * @throws IOException if it could not read requested number of bytes 
	 * for any reason (including EOF)
	 */
	public static void readFully(InputStream in, byte buf[], int off, int len) throws IOException {
		int toRead = len;
		while (toRead > 0) {
			int ret = in.read(buf, off, toRead);
			if (ret < 0) {
				throw new IOException("Premature EOF from inputStream");
			}
			toRead -= ret;
			off += ret;
		}
	}

	/** Reads len bytes in a loop using the channel of the stream
	 * @param fileChannel a FileChannel to read len bytes into buf
	 * @param buf The buffer to fill
	 * @param off offset from the buffer
	 * @param len the length of bytes to read
	 * @throws IOException if it could not read requested number of bytes 
	 * for any reason (including EOF)
	 */
	public static void readFileChannelFully(FileChannel fileChannel, byte buf[], int off, int len) throws IOException {
		int toRead = len;
		ByteBuffer byteBuffer = ByteBuffer.wrap(buf, off, len);
		while (toRead > 0) {
			int ret = fileChannel.read(byteBuffer);
			if (ret < 0) {
				throw new IOException("Premeture EOF from inputStream");
			}
			toRead -= ret;
			off += ret;
		}
	}

	/** Similar to readFully(). Skips bytes in a loop.
	 * @param in The InputStream to skip bytes from
	 * @param len number of bytes to skip.
	 * @throws IOException if it could not skip requested number of bytes 
	 * for any reason (including EOF)
	 */
	public static void skipFully(InputStream in, long len) throws IOException {
		while (len > 0) {
			long ret = in.skip(len);
			if (ret < 0) {
				throw new IOException("Premature EOF from inputStream");
			}
			len -= ret;
		}
	}

	/**
	 * Close the Closeable objects and <b>ignore</b> any {@link IOException} or 
	 * null pointers. Must only be used for cleanup in exception handlers.
	 * @param log the log to record problems to at debug level. Can be null.
	 * @param closeables the objects to close
	 */
	public static void cleanup(Log log, java.io.Closeable... closeables) {
		for (java.io.Closeable c : closeables) {
			if (c != null) {
				try {
					c.close();
				} catch (IOException e) {
					if (log != null && log.isDebugEnabled()) {
						log.debug("Exception in closing " + c, e);
					}
				}
			}
		}
	}

	/**
	 * Closes the stream ignoring {@link IOException}.
	 * Must only be called in cleaning up from exception handlers.
	 * @param stream the Stream to close
	 */
	public static void closeStream(java.io.Closeable stream) {
		cleanup(null, stream);
	}

	/**
	 * Closes the socket ignoring {@link IOException} 
	 * @param sock the Socket to close
	 */
	public static void closeSocket(Socket sock) {
		// avoids try { close() } dance
		if (sock != null) {
			try {
				sock.close();
			} catch (IOException ignored) {
			}
		}
	}

	/** /dev/null of OutputStreams.
	 */
	public static class NullOutputStream extends OutputStream {
		public void write(byte[] b, int off, int len) throws IOException {
		}

		public void write(int b) throws IOException {
		}
	}
}
